After reading all the theories pages after page, the couple of things that I think might actually happen are:
1) Raghav's dealing and Mandar's dealing are two different stories but somehow they ended up in the same place.
2)Mandar was definitely into some shady business and had connections with Ved. And maybe Ved is somehow responsible for him to end up there when some gang war of Raghav was going on.
3)Baba sent him out for some work par ussi beech mein Ved ka or business/gang related kisi ka call aaya hoga and that's how he ended up being on that sunsaan sadak.
4) Mandar's story consists of Devyani,I don't know how. Par if Raghav Pallavi team up together and decide to uncover what actually happened on Dec 1,2018 then we might get some clearance.
5) If Mandaar actually turns out to be alive and was faking his death all these while, then whatever respect Pallavi had for him would be over. She'd be truly able to move on in her life from the past. But that will meddle with the entire purpose of this show because:
i) The whole theme of a widow moving on in her life would be cancelled if she was never a widow to begin with.
ii) Mandar alive and back with his family would dilute the connection and significance of D family in Pallu's life.
Personally I'm all up for Mandaar being alive and getting Pallu away from D family drama. But knowing the original intention of the show was a widow getting remarried and her husband accepting her with the D family,will CVs take this route?